1. Field of the Invention The present invention relates to a technical field of an electro-optical apparatus such as an active matrix driving liquid crystal apparatus driven by thin film transistors (hereinafter also referred to as TFTs) or the like, and also to an electronic device using the same. More particularly, the present invention relates to an electro-optical apparatus in which data lines are driven at a high frequency by a data line driving circuit provided on a TFT array substrate in response to a control signal such as a clock signal, and also an electronic device using the same.
2. Description of Related Art
In conventional electro-optical apparatuses such as an active-matrix driving TFT liquid crystal apparatus, a great number of scanning lines and data lines are formed in horizontal and vertical directions, respectively, on a TFT array substrate, and a great number of pixel electrodes are formed at respective intersections of the scanning lines and the data lines. In some cases, in addition to the above elements, other elements are also formed on the TFT array substrate, such as data signal supply means including a data line driving circuit and a sampling circuit or the like and serving to supply a data signal to the data lines, and also a scanning signal supply means including a scanning line driving circuit or the like and serving to supply a scanning signal to the scanning lines.
In this case, a control signal such as a data line side reference clock signal which activates a data line driving circuit indicating a time reference for supplying a data signal, an image signal which corresponds to the content of images to be displayed and which is used as a basis on which the data signal is produced, and positive and negative constant electric potential power-supply or the like are supplied to the data signal supply means via external input terminals and wiring provided on the TFT array substrate, respectively. Similarly, a scanning line side reference clock signal which activates a scanning line driving circuit indicating a time reference for supplying a scanning signal, and positive and negative constant electric potential power-supply are supplied to the scanning signal supply means via external input terminals and wiring provided on the TFT array substrate. In the scanning signal supply means, for example, the scanning line driving circuit supplies a scanning signal over the scanning lines on the line-by-line basis in accordance with the scanning line side reference clock signal In response, in the data signal supply means, the data line driving circuit drives the sampling circuits, which serve to sample the input image signal, one by one in accordance with the timing indicated by the data line side reference clock signal. As a result, a data signal is supplied from the sampling circuits over the data lines. The respective TFTs whose gate is connected to one of the scanning lines turn on in response to receipt of the scanning signal supplied via the scanning lines. As a result, the data signal is supplied to the pixel electrodes via the corresponding TFTs and thus an image is displayed on the respective pixels.
In recent liquid crystal apparatuses, in particular in those for use in a liquid crystal projector, the frequency of serial image signals becomes increasingly high with the increase in the resolution of the image displayed. For example, the dot frequency of the image signal in the XGA display mode or SXGA display mode employed in recent high-resolution displays for personal computers is about 65 MHZ and 135 MHZ, respectively, which are much higher than the dot frequency in the conventional VGA mode (about 30 MHZ). As a result, a very high frequency is also required for the data line side reference clock signal supplied to the data signal supply means.
The increase in the frequency of the reference clock signals results in generation of high-frequency clock noise, which cannot be neglected, to achieve a high-quality display image. With the conventional technique of supplying a relatively low-frequency data line side reference clock signal to the data line driving circuit to drive the sampling circuit, if the frequency of the clock signal is simply increased, high-frequency clock noise intrudes into the image signal input to the sampling circuit or into the data signal output from the sampling circuit, and thus the data signal supplied to the data lines is degraded by the noise. The degradation in the data signal input to the respective pixels results in degradation in the image displayed by the respective pixels. For example, when a halftone image is displayed by the respective pixels, if noise as small as about 10 mV intrudes into the image signal, then visual noise appears in the displayed image. This is because, in the case of the halftone image, unlike the two-level display in which only white and black levels are displayed by applying a highest or lowest driving voltage (for example, 5 and 0 V) to a liquid crystal, the transmittance of the liquid crystal is very sensitive to the change in the voltage applied to the liquid crystal. Therefore, high-frequency clock noise is an important problem which has to be solved to realize a high-precision multi-level gray scale display.
If the number of phases into which the original image signal is serial-to-parallel converted is increased, it is possible to reduce the frequency of the image signals supplied to the sampling circuit. However, in this case, it is required to increase the number of external input terminals, which are provided on a substrate of a liquid crystal apparatus so as to input an image signal, depending on the number of phases of the serial-to-parallel-converted image signal. For example, when the serial-to-parallel conversion is performed into six phases, six external input terminals for inputting the image signal are required. In the case where the serial-to-parallel conversion is performed into twelve phases, twelve external input terminals are required. Furthermore, it is also required that there be as many wirings for transferring the image signal, input via the external input terminals, to the sampling circuit as there are serial-to-parallel conversion phases. As a result, the wirings for the image signal occupy a large area on the substrate of the liquid crystal apparatus. This makes it difficult to allocate a proper area on the substrate for forming the data signal supply means including the sampling circuit, the data line driving circuit, or the like. If wirings for control signals such as a clock signal are formed on a substrate in such a manner that they extend from an edge of the substrate where external input terminals are formed to one side of the data line driving circuit, and many wirings for image signals are formed on a substrate in such a manner that they extend to the other side if the data line driving circuit as is employed in the conventional technique, then the number of wirings extended to each side becomes very different between two sides of the data line driving circuit, so that the wiring balance in the surrounding of the data line driving circuit becomes quite bad (that is, wirings are concentrated on only one side). It is possible to increase the size of the substrate of the liquid crystal apparatus so that the wiring area and the data line driving circuit are disposed in the increased area. However, the increase in the size does not meet the requirement in the art of the liquid crystal apparatus for achievement of a large image display area using a limited size of substrate.
In view of the above, it is an object of the present invention to provide an electronic device including an electro-optical apparatus capable of displaying a high-quality image according to an input image signal or a data signal generated from the image signal with suppressed high-frequency clock noise.
It is another object of the present invention to provide a liquid crystal apparatus capable of displaying a high-quality image and also an electronic device provided with such a liquid crystal apparatus, in which a great number of wirings and a great number of external input terminals corresponding to a great number of serial-to-parallel-converted phases of an image signal are disposed in a well-balanced fashion and negative effects of high-frequency clock noise arising from control signals, such as a high-frequency clock signals, on the image signal are suppressed.
According to a first aspect of the present invention, to achieve the above objects, there is provided an electro-optical apparatus comprising a substrate and elements formed on the substrate, the elements including: a plurality of scanning lines; a plurality of data lines intersecting the plurality of scanning lines; a plurality of switching elements connected to the plurality of scanning lines and data lines; a plurality of pixel electrodes connected to the plurality of switching elements; data signal supply means for supplying, in response to a clock signal, a data signal corresponding to an image signal to the plurality of data lines; an image signal line for supplying the image signal input via a first external input terminal to the data signal supply means; a clock signal line for supplying the clock signal input via a second external input terminal to the data signal supply means; and an electrically conductive line maintained at a constant electric potential for shielding the image signal line from the clock signal line.
In accordance with these features of the invention, the image signal is input via the first external input terminal and supplied to the data signal supply means via the image signal line extending on the substrate. In parallel to the image signal, the clock signal is input via the second external input terminal and supplied to the data signal supply means via the clock signal line extending on the substrate. In response to this clock signal, the data signal supply means including, for example, a data line driving circuit and a sampling circuit or the like provided on a first substrate supplies the data signal corresponding to the image signal on the basis of the clock signal to the plurality of data lines. Herein, the image signal line is electrically shielded from the clock signal line by means of the electrically conductive line extending on the substrate and maintained at the constant electric potential, so that intrusion of high-frequency clock noise from the clock signal line to the image signal line is suppressed even when the clock signal has a high frequency.
On the other hand, a scanning signal is supplied to the switching elements via scanning lines by scanning signal supply means including a scanning line driving circuit formed on or connected to the substrate. Data signals corresponding to the image signals, whose clock noise is suppressed in the above-described manner, are supplied to respective switching elements via corresponding data lines. The voltages applied to the respective pixel electrodes by the data signals supplied via the switching elements vary in accordance with the applied data signals, and liquid crystals corresponding to the respective pixel electrodes are driven by the applied voltage. As a result, a high-quality image with a high resolution is displayed in accordance with the serial high-frequency image signal under the control of the high-frequency clock signal without having any or significant degradation in the image quality caused by high-frequency clock noise.
In this first aspect of the invention, the electrically conductive line preferably includes a part made up of a constant electric potential line for supplying a constant electric potential power-supply to the data signal supply means.
In accordance with these features of the invention, because the electrically conductive line includes the part made up of the constant electric potential line for supplying the constant electric potential power-supply to the data signal supplying means, it is possible to share an external input terminal and a wiring itself . In other words, it is possible to realize the electrically conductive line by extending the constant electric potential line. Thus it is possible to achieve simplification in structure and a reduction in space. Furthermore, it becomes very easy to maintain the electrically conductive line at a constant electric potential.
In another preferred mode of the first aspect of the present invention, the constant electric potential line includes first and second constant electric potential lines for supplying different constant electric potential power-supply to the data signal supply means, the part of the electrically conductive line formed of the first constant electric potential line surrounds the image signal line on the first substrate, and the part of the electrically conductive line formed of the second constant electric potential line surrounds the clock signal line on the substrate.
In accordance with these features of the first aspect of the invention, on the substrate, the image signal line is surrounded, for example, by the part of the electrically conductive line made up of the first constant electric potential line for supplying a negative power supply equal to a ground electric potential. On the other hand, on the substrate, the clock signal line is surrounded, for example, by the part of the electrically conductive line made up of the second constant electric potential line for supplying a positive power-supply. Thus, on the first substrate, the image signal line is doubly shielded, from the clock signal lines.
In still another preferred mode according to the first aspect of the invention, the data signal supply means includes a sampling circuit for sampling the image signal, and also includes a data line driving circuit which receives electric power supplied via the constant electric potential line and which drives the sampling circuit in accordance with the clock signal, and the image signal line and the clock signal line extend on the substrate in directions opposite to each other with respect to the data line driving circuit.
In accordance with these features of the invention, the image signal is sampled by the sampling circuit in the scanning signal supply means. In accordance with the clock signal, the sampling circuit is driven by the data line driving circuit which receives electric power via the constant electric potential line. The resultant sampled image signal is supplied as a data signal over the data lines. In this preferred mode, as described above, the image signal line and the clock signal line are formed such that they extend on the substrate in directions opposite to each other with respect to the data line driving circuit. In general, electromagnetic waves decay with distance, depending on the presence of an obstacle. Thus, electromagnetic waves applied to the image signal line from the clock signal line decrease depending on the distance between the image signal line and the clock signal line, and also depending on the presence of the data line driving circuit. Therefore, even when the clock signal has a high frequency, intrusion of high-frequency clock noise from the clock signal line to the image signal line is suppressed.
In a further preferred mode according to the first aspect of the present invention, the first and second external input terminals are disposed in a peripheral area of the substrate such that they are spaced from each other by a predetermined distance and a third external input terminal for inputting the constant electric potential power-supply to the constant electric potential line is disposed between the first and second external input terminals.
That is, in accordance with these features of the present invention, the first and second external input terminals are disposed in the peripheral area of the substrate such that they are spaced from each other by the predetermined distance via the third external input terminal, and more preferably, they are spaced as far apart as possible from each other within the area available for formation of the external input terminals on the periphery of the substrate. As a result of the above arrangement, the image signal line encounters less intrusion of high-frequency clock noise from the clock signal line compared with the case where the image signal line and the clock signal line are disposed close to each other.
In a yet further preferred mode according to the first aspect of the present invention, on the substrate, the electrically conductive line is extended such that the electrically conductive line surrounds an image display area defined by the plurality of pixel electrodes, and also surrounds the plurality of data lines.
That is, in accordance with these features of the present invention, because the image display area and the plurality of data lines are surrounded by the electrically conductive line on the substrate, the image display area and the plurality of data lines are shielded from the clock signal line. Thus, intrusion of high-frequency clock noise into the data signal output from the data signal supply means and to the data signal input to the switching elements or the pixel electrodes is suppressed.
In a different preferred mode according to the first aspect of the present invention, an electro-optical material is disposed between the substrate and an opposite substrate, and a light shielding frame is disposed on at least either the substrate or the opposite substrate, and furthermore the electrically conductive line includes a part formed on the substrate at a location opposite to the light shielding frame and along the light shielding frame.
That is, in accordance with these features of the present invention, because the electrically conductive line is disposed under the light shielding frame formed on the opposite substrate, the required space on the TFT array substrate is reduced. More specifically, it is possible to find a sufficient area on the periphery of the substrate for forming the scanning line driving circuit and the data line driving circuit without having a reduction in the effective image display area of the electro-optical apparatus caused by formation of the electrically conductive line.
In a different preferred mode according to the first aspect of the present invention, the electrically conductive line and the data line are formed of the same metal material with a low resistance.
In accordance with these features of the present invention, because the electrically conductive line is formed of the same metal material with a low resistance as that used to form the data lines, such as Al (aluminum), the electrically conductive line may extend along a long distance while maintaining the resistance of the electrically conductive line to a level low enough for practical use. That is, it becomes possible to extend the electrically conductive line in a zigzag fashion between other wirings or various circuits along a long distance or over a wide area including the image display area, without encountering a reduction in the shielding effects caused by the increase in resistance. Thus, it is possible to enhance the overall shielding effects using a rather simple structure. Furthermore, it is possible to form the electrically conductive line and the data lines using the same metal material with a low resistance in the same process during the production process of the electro-optical apparatus. That is, the increase in the processing steps resulting from the introduction of the electrically conductive line can be minimized.
In a different preferred mode according to the first aspect of the present invention, the part of the electrically conductive line formed between the image signal line and the clock signal line, the image signal line, and the clock signal line are formed from the same low-resistance metal layer formed in a single same plane parallel to the substrate.
In accordance with these features of the present invention, because the part of the electrically conductive line formed between the image signal line and the clock signal line, the image signal line, and the clock signal line are formed in the single same plane parallel to the substrate, it is possible to achieve further improved shielding effects. Herein, the xe2x80x9cformation in the same planexe2x80x9d includes the case where the above lines are formed directly on the substrate and also the case where the above-described lines are formed on an insulating layer formed on the substrate or the case where the above-described lines are formed on an interlayer insulating layer formed on a semiconductor layer in which TFTs and switching elements or the like are formed. Furthermore, because the electrically conductive line, the image signal line, and the clock signal line are formed from the same low-resistance metal layer, such as an Al layer, at the same time during the process of producing the electro-optical apparatus, the increase in the production processing steps caused by the introduction of the electrically conductive line is minimized.
In a preferred mode according to the first aspect of the present invention, there is provided a capacitance line for adding a predetermined magnitude of capacitance to the pixel electrode, wherein the capacitance line is connected to the electrically conductive line.
In accordance with these features of the present invention, because the predetermined magnitude of capacitance is added by the capacitance line to the pixel electrode, it becomes possible to display a high-precision image even when the duty ratio is small. Furthermore, because the capacitance line is connected to the electrically conductive line, it is possible to prevent negative effects of the variation in electric potential of the capacitance line on the switching elements and pixel electrodes. Furthermore, the electrically conductive line can also serve as a wiring for maintaining the capacitance line at a constant electric potential. Still furthermore, for example, the third external input terminal or the external input terminal for the electrically conductive line may be employed also as an external input terminal for inputting the constant electric potential at which the capacitance line is maintained.
According to a second aspect of the present invention, there is provided an electro-optical apparatus comprising a substrate and elements formed on the substrate, the elements including: a plurality of data lines; a plurality of scanning lines crossing the plurality of data lines; a plurality of switching elements connected to the plurality of data lines and the plurality of scanning lines; a plurality of pixel electrodes connected to the plurality of switching elements; a plurality of image signal lines supplied with image signals; a plurality of control signal lines supplied with control signals including a clock signal; and data signal supply means which receives the image signals and the control signals via the image signal lines and the control signal lines, and which supplies data signals corresponding to the image signals to the plurality of data lines in accordance with the control signals; wherein, on the substrate, a first group of image signal lines of the plurality of image signal lines extend to one side of the data signal supply means and a second group of image signal lines of the plurality of image signal lines extend, to the opposite side of the data signal supply means, and the electro-optical apparatus further comprises at least one electrically conductive line which is formed on the substrate so as to electrically shield the first and second groups of image signal lines from the plurality of control signal lines.
In this second aspect of the present invention, the image signals are input to the data signal supplying means via the image signal lines. In parallel with the image signals, the control signals including a clock signal and an enable signal or the like are supplied to the data signal supply means via the control signal lines. In response, the data signal supplying means including a data line driving circuit and a sampling circuit, for example, supplies the data signals corresponding to the image signals to the plurality of data lines on the basis of the control signals. The image signal lines are electrically shielded by the electrically conductive line formed on the substrate from the respective control signal lines including the clock signal line and the enable signal line or the like. Therefore, even when the clock signal has a high frequency, intrusion of high-frequency clock noise from the control lines such as a clock signal line to the image signal lines is suppressed.
On the other hand, a scanning signal is supplied to the switching elements via scanning lines from scanning signal supply means, including a scanning line driving circuit formed on or connected to the substrate. In parallel with this, data signals corresponding to the image signals, whose clock noise is suppressed in the above-described manner, are supplied to the respective switching elements via corresponding data lines. Thus, the voltages applied to the pixel electrodes vary in accordance with the data signals supplied via the switching elements and liquid crystals corresponding to the respective pixel electrodes are driven by the applied voltage.
Therefore, even when it is required to display a high-resolution image in accordance with image signals converted from a serial form into a parallel form consisting of a plurality of phases, it is possible to display the image with high quality without having any or significant degradation in the image quality caused by high-frequency clock noise. Furthermore, on the substrate, the first group of image signal lines extend to one side of the data signal supply means while the second group of image signal lines extend to the opposite side of the data signal supply means. Thus, it is possible to reduce the frequency of the image signals supplied to the data signal supply means by increasing the number of phases into which the original image signal is serial-to-parallel converted, for example, to 12 or 24 phases. The great number of image signal lines corresponding to the increased number of phases are disposed at both sides of the data signal supply means such that they are distributed in a well-balanced fashion. This makes it possible to easily find an area on the substrate for use as an area in which the sampling circuit or the data signal supply means including the sampling circuit and the data line driving circuit or the like is formed. Thus it becomes possible to form a large image display area on a substrate with a limited size.
In a preferred mode according to the second aspect of the present invention, the electrically conductive line shields the first and second groups of image signal lines from at least a high-frequency control signal line of the plurality of control signal lines, the high-frequency control signal line having a repetition period shorter than the horizontal scanning period of the image signals.
That is, in accordance with these features of the present invention, the image signal lines are electrically shielded from the high-frequency control signal line for supplying a high-frequency control signal (such as a clock signal and an enable signal) of the plurality of control signal lines by the electrically conductive line . Therefore, even when the clock signal has a high frequency, intrusion of high-frequency clock noise from the high-frequency control signal line to the image signal lines is suppressed. On the other hand, a low-frequency control signal (such as a start signal for a shift register in the data line driving circuit) does not cause high-frequency noise to the image signals or the data signals. Therefore, the low-frequency control signal line for supplying such a control signal may or may not be shielded by an electrically conductive line.
In another preferred mode according to the second aspect of the present invention, of the plurality of control signal lines, a low-frequency control signal line for supplying a low-frequency control signal having a repetition period which is, at least, not shorter than the horizontal scanning period of the image signals is disposed together with the electrically conductive line between the first and second groups of image signal lines and the high-frequency control signal line.
In accordance with these features of the present invention, of the image signal lines included in the first or second image signal line groups, an image signal line closest to the high-frequency control signal line is physically spaced apart and electrically shielded from the high-frequency control signal line by at least two wirings, including the low-frequency control signal line and the electrically conductive line. That is, the low-frequency control signal line for supplying a low-frequency control signal (such as a start signal for the shift register in the data line driving circuit) which does not cause high-frequency noise to the image signals or the data signals is disposed together with the electrically conductive line between the high-frequency control signal line and the image signal lines, thereby further reducing the negative effects, such as clock noise, of the high-frequency control signal line on the image signal lines. In general, electromagnetic waves decay with distance, depending on the presence of an obstacle. Thus, electromagnetic waves applied to the image signal lines from the high-frequency control signal line can be reduced by disposing as many electrically conductive lines and low-frequency control signal lines between the control signal lines and the image signal lines. Disposing a low-frequency control signal line, in addition to an electrically conductive line, between the high-frequency control signal line and the image signal lines results in efficient use of the space on the substrate and also a reduction in noise.
In still another preferred mode according to the second aspect of the present invention, the electro-optical device further comprises external input terminals formed in a peripheral area of the substrate, the external input terminals including: a plurality of first external input terminals connected to the first group of image signal lines, the plurality of first external input terminals serving to receive the respective image signal from an external image signal source; a plurality of second external input terminals connected to the second group of image signal lines, the plurality of second external input terminals serving to receive the respective image signal from the external image signal source; a plurality of third external input terminals connected to the control signal lines, the plurality of third external input terminals serving to receive the control signals from an external control signal source; and a plurality of fourth external input terminals connected to the electrically conductive lines, wherein the third external input terminals are disposed between the first and second external input terminals, and the fourth external input terminals are disposed between the first and third external input terminals and between the third and second external input terminals.
In accordance with these features of the present invention, as described above, the plurality of third external input terminals connected to the control signal lines are disposed on the periphery of the substrate such that they are located between the plurality of first and second external input terminals connected to the first and second groups of image signal lines, respectively. That is, in the peripheral area of the substrate where the first to fourth external input terminals are formed, the plurality of third external input terminals connected to the control signal lines are disposed in a central area in a concentrated fashion, and the first and second external input terminals connected to the first and second groups of image signal lines, respectively, are disposed at both sides of the third external input terminals. The fourth external input terminals connected to the electrically conductive lines are disposed between the first and third external input terminals and between the third and second external input terminals. That is, the first and second groups of image signal lines are spaced, on the substrate, apart from the control signal lines, and the electrically conductive lines are disposed in this space. This arrangement makes it possible to effectively prevent the image signals from encountering noise arising from the control signals such as a clock signal before the image signals are input to the electro-optical apparatus. Instead of employing the above arrangement according to the present invention, if the plurality of external input terminals connected to the image signal lines and those connected to the control signal lines are disposed in a mixed fashion in the same area or disposed at locations close to each other, then the image signals and the control signals are input to the electro-optical apparatus along wirings adjacent or close to each other, and thus noise such as clock noise intrudes into the image signals. However, in the present invention, intrusion of high-frequency clock noise from the clock signal line to the image signal lines is suppressed before and after the image signals are input to the electro-optical apparatus. More preferably, the first and second external input terminals are disposed at locations shifted to both side ends to as large a degree as possible in areas available for formation of the external input terminals on the periphery of substrate, and the first and second external input terminals are spaced as far apart as possible from the third external input terminals disposed between them, so that the fourth external input terminals connected to the electrically conductive lines are disposed in the spaces.
In a further preferred mode according to the second aspect of the present invention, the electrically conductive line shields the first and second groups of image signal lines from a high-frequency control signal line of the plurality of control signal lines, for supplying the high-frequency control signal having a repetition period which is, at least, shorter than the horizontal scanning period of the image signals, wherein, of the third external input terminals, the one adjacent to the fourth external input terminals is connected to a low-frequency control signal line of the plurality of control signal lines for supplying a low-frequency control signal having a repetition period which is, at least, not shorter than the horizontal scanning period of the image signals.
In accordance with these features of the present invention, the image signal lines are electrically shielded by the electrically conductive lines from the high-frequency control signal line. In particular, of the third external input terminals connected to the control signal lines, the third external input terminal located adjacent the fourth external input terminals connected to the electrically conductive lines is connected to the low-frequency control signal line. As a result, the image signal lines are physically spaced apart and electrically shielded from the high-frequency control signal line by at least two wirings including the low-frequency control signal line and the electrically conductive line.
In a yet further preferred mode according to the second aspect of the present invention, the electrically conductive line includes a part made up of a data line which drives a constant electric potintial lilne for supplying a power-supply which drives data lines of a constant electric potential to the data signal supplying means.
In accordance with these features of the present invention, because the electrically conductive line includes the part made up of the data line which drives a constant electric potential line for supplying a power supply which drives data lines of a constant electric potential to the data signal supplying means, it is possible to share an external input terminal and a wiring independent of the electrically conductive line and the constant electric potential line. In other words, it is possible to realize the electrically conductive line by extending the constant electric potential line. Thus it is possible to achieve simplification in structure and a reduction in space. Furthermore, it becomes very easy to maintain the electrically conductive line at a constant electric potential.
In a different preferred mode according to the second aspect of the present invention, the data line which drives a constant electric potential line includes first and second constant electric potential lines for supplying different constant electric potential power-supply to the data signal supplying means, the part of the electrically conductive line formed of the first constant electric potential line surrounds the first and second groups of image signal lines, on the substrate, and the part of the electrically conductive line formed of the second constant electric potential line surrounds the control signal lines on the first substrate.
In accordance with these features of the present invention, the first and second groups of image signal lines are surrounded on the substrate, for example, by the part of the electrically conductive line made up of the first constant electric potential line for supplying a negative power supply equal to a ground electric potential. The control signal lines are surrounded on the substrate, for example, by the part of the electrically conductive line made up of the second constant electric potential line for supplying a positive power supply. Thus, the image signal lines are doubly shielded from the control signal lines on the first substrate.
In a different preferred mode according to the second aspect of the present invention, the electrically conductive line is extended such that, on the substrate, the electrically conductive line surrounds an image display area defined by the plurality of pixel electrodes and also surrounds the plurality of data lines.
In accordance with these features of the present invention, because the image display area and the plurality of data lines are surrounded by the electrically conductive line on the substrate, the image display area and the plurality of data lines are shielded from the control signal lines such as the clock signal line. Thus, intrusion of high-frequency clock noise into the data signal output from the data signal supply means and to the data signal or the like input to the switching elements or the pixel electrodes is suppressed.
In a different preferred mode according to the second aspect. of the present invention, the electro-optical apparatus further comprises an opposite substrate located opposite to the substrate; and a light shielding frame disposed, along the contour of the image display area, on at least either the substrate or the opposite substrate, wherein the electrically conductive line includes a part formed on the substrate at a location opposite to the light shielding frame and along the light shielding frame.
In accordance with these features of the present invention, because the electrically conductive line is disposed on the substrate and under the light shielding frame, the required space on the TFT array substrate is reduced. More specifically, it is possible to find a sufficient area on the periphery of the substrate for forming the scanning line driving circuit and the data line driving circuit without having a reduction in the effective display area of the liquid crystal apparatus caused by formation of the electrically conductive line.
In a different preferred mode according to the second aspect of the present invention, the electrically conductive line and the data line are formed of the same metal material with a low resistance.
In accordance with these features of the present invention, because the electrically conductive line is formed of the same metal material with a low resistance as that used to form the data lines, such as Al (aluminum), the electrically conductive line may be extended along a long distance while maintaining the resistance of the electrically conductive line to a level low enough for practical use. That is, it becomes possible to extend the electrically conductive line in a zigzag fashion between other wirings or various circuits or the like along a long distance or over a wide area including the image display area or the like, without encountering a reduction in the shielding effects caused by the increase in resistance. Thus, it is possible to enhance the overall shielding effects using a rather simple structure. Furthermore, it is possible to form the electrically conductive line and the data lines using the same metal material with a low resistance in the same process during the production process of the electro-optical apparatus. That is, the increase in the processing steps resulting from the introduction of the electrically conductive line can be minimized.
In a different preferred mode according to the second aspect of the present invention, there is provided a capacitance line for adding a predetermined magnitude of capacitance to the pixel electrodes, wherein the capacitance line is connected to the electrically conductive line.
In accordance with these features of the present invention, because the predetermined magnitude of capacitance is added by the capacitance line to the pixel electrode, it becomes possible to display a high-precision image even when the duty ratio is small. Furthermore, because the capacitance line is connected to the electrically conductive line, it is possible to prevent negative effects from the variations in electric potential of the capacitance line on the switching elements and pixel electrodes. Furthermore, the electrically conductive line can also serve as a wiring for maintaining the capacitance line at a constant electric potential. Still furthermore, for example, the third external input terminal or the external input terminal for the electrically conductive line may be employed also as an external input terminal for inputting the constant electric potential at which the capacitance line is maintained.
In a different preferred mode according to the second aspect of the present invention, the electro-optical apparatus further comprises scanning signal supply means formed on the substrate, for supplying a scanning signal to said plurality of scanning lines line by line, wherein the electrically conductive line includes a part made up of a scanning line that drives a constant electric potential line for supplying a power supply which drives scanning lines of a constant electric potential to the scanning signal supply means.
In accordance with these features of the present invention, the image signal lines are electrically shielded from the control signal lines by the part of the electrically conductive line made up of the scanning line that drives a constant electric potential line. Therefore, even when the clock signal has a high frequency, intrusion of high-frequency clock noise from the control signal line to the image signal lines is suppressed.
In a different preferred mode according to the second aspect of the present invention, the scanning signal supply means is formed at both sides of an image display area defined by the plurality of pixel electrodes, and the part of the electrically conductive line made up of the scanning line that drives a constant voltage line is extended such that the part of the electrically conductive line surrounds the image display area and the plurality of data lines on the substrate and such that the scanning-line power-supply is supplied to the scanning line supply means in a redundant fashion.
In accordance with these features of the present invention, on the substrate, the image display area and the plurality of data lines are surrounded by the part of the electrically conductive line made up of the scanning line which drives a constant electric potential line so that the image display area and the plurality of data lines are also shielded by the control signal lines such as the clock signal line. Thus, intrusion of high-frequency clock noise or the like into the data signal output from the data signal supply means and to the data signal or the like input to the switching elements or the pixel electrodes is suppressed. Furthermore, because the part of the electrically conductive line made up of the scanning line that drives a constant electric potential line is extended such that the scanning-line driving power-supply is supplied in a redundant fashion to the scanning line supply means disposed at both sides of the image display area, even if breakage or disconnection occurs in the part of the electrically conductive line made up of the scanning line that drives a constant electric potential line or in other parts, the disconnection does not result in a fatal failure of the apparatus.
In a different preferred mode according to the second aspect of the present invention, the data signal supply means includes: a sampling circuit for sampling the image signal; and a data line driving circuit for driving the sampling circuit in accordance with the control signal, wherein the image signal lines included in the first group of image signal lines and the image signal lines included in the second group of image signal lines extend alternately in an area between the data line driving circuit and the sampling circuit at least every one or more image signal lines from both sides of the data line driving circuit in a comb fashion.
In accordance with these features of the present invention, the image signal lines included in the first group of image signal lines (for example, image signal lines VID1, VID3, VID5, VID7, . . . corresponding to the odd-numbered data lines) and the image signal lines included in the second group of image signal lines (for example, image signal lines VID2, VID4, VID6, VID8, . . . corresponding to the even-numbered data lines) extend alternately at least every one or more image signal lines from both sides of the data line driving circuit in the comb fashion. This allows the image signal lines and the data lines to be disposed in a systematic and well-balanced fashion around the data line driving circuit.
In a different preferred mode according to the second aspect of the present invention, the data signal supply means inverts the polarity of the voltage of the data signal every data line, wherein the image signal lines included in the first group of image signal lines and the image signal lines included in the second group of image signal lines extend, in a comb form, alternately every two image signal lines corresponding to adjacent two data lines from both sides of the data line driving circuit.
In accordance with these features of the present invention, the polarity of the voltage of the data signal is inverted line by line by the data signal supply means in a manner called 1S inversion, or dot inversion, thereby suppressing flicker in the displayed image. In this mode, the image signal lines included in the first group of image signal lines (for example, image signal lines VID1, VID2, VID5, VID6, . . . corresponding to two adjacent data lines, every four data lines) and the image signal lines included in the second group of image signal lines (for example, image signal lines VID3, VID4, VID7, VID8, . . . corresponding to two adjacent data lines, every four data lines) extend alternately every two image signal lines corresponding to adjacent two data lines, from both sides of the data line driving circuit in the comb fashion. As a result, the image signals supplied to two adjacent image signal lines become opposite in polarity to each other. Thus, noise components arising from the same noise source are canceled out between two adjacent image signal lines, and thus noise is suppressed.
The electro-optical apparatus according to the first or second aspect of the present invention may be used in an electronic device.
The electronic device provided with the electro-optical apparatus according to the present invention has the advantage in that high-frequency clock noise or the like is suppressed, and a high-quality image can be displayed.
These and other features and advantages of the present invention will become more apparent from the following detailed description referring to preferred embodiments.